What are the causes of atrial fibrillation (a-fib)?

Causes of Atrial Fibrillation

Atrial fibrillation is primarily caused by structural heart disease, cardiovascular risk factors, and age-related changes, with valvular heart disease, hypertension, and coronary artery disease being the most common underlying conditions. 1

Cardiovascular Conditions Associated with AF

Structural Heart Disease

• Valvular heart disease: Most commonly mitral valve disease 2, 1
• Coronary artery disease: Causes ischemia and scarring 2, 1
• Hypertension: Particularly when left ventricular hypertrophy is present, causing ventricular diastolic abnormalities and increased left atrial pressure 2, 1
• Cardiomyopathies:
  • Hypertrophic cardiomyopathy
  • Dilated cardiomyopathy
  • Restrictive cardiomyopathies (e.g., amyloidosis, hemochromatosis, endomyocardial fibrosis) 2, 1
• Congenital heart disease: Especially atrial septal defect in adults 2, 1
• Other cardiac conditions:
  • Mitral valve prolapse with or without mitral regurgitation
  • Calcification of the mitral annulus
  • Cardiac tumors
  • Constrictive pericarditis
  • Idiopathic dilation of the right atrium 2, 1

Non-Cardiac Conditions

• Metabolic disorders:
  • Hyperthyroidism 2, 1
  • Diabetes mellitus (present in 20% of AF patients) 1
• Obesity: Found in 25% of AF patients 1
• Pulmonary conditions:
  • Sleep apnea syndrome 2, 1
  • Chronic obstructive pulmonary disease (10-15% of AF patients) 1
  • Pulmonary embolism 2, 1
• Chronic kidney disease: Present in 10-15% of AF patients 1

Acute Temporary Causes

• "Holiday heart syndrome": Alcohol intake 2, 1
• Perioperative: Cardiac or thoracic surgery 2
• Trauma: Electrocution 2, 1
• Acute cardiac conditions:
  • Myocardial infarction (portends worse prognosis) 2, 1
  • Pericarditis
  • Myocarditis 2, 1
• Infections: Can trigger AF through systemic inflammatory response, oxidative stress, and hemodynamic alterations 1

Pathophysiological Mechanisms

Structural Remodeling

• Atrial fibrosis: Progressive structural changes in atrial tissue 1
• Loss of atrial muscle mass: Age-dependent (0.5-1.0% per year) 1
• Inflammation and hypertrophy: Creates heterogeneous conduction pathways 1

Electrical Abnormalities

• Enhanced automaticity: Focal AF 2
• Conduction abnormalities: Leading to reentry circuits 2
• Ion-channel dysfunction: Genetic or acquired changes in ion channel expression 1
• Altered calcium homeostasis: High atrial rates elevating diastolic calcium levels 1

Autonomic Influences

• Vagal predominance: Often occurs at night or after meals 2
• Sympathetic predominance: Typically occurs during daytime 2
• Balance between sympathetic and vagal influences: Important predictor of AF 2

Lone and Familial AF

• Lone AF: Occurs without demonstrable underlying disease in approximately 30-45% of paroxysmal cases and 20-25% of persistent cases 2, 1
• Familial AF: Genetic susceptibility, with specific chromosomal loci linked to AF in some families 2, 1

Clinical Implications

When evaluating a patient with AF, it's crucial to identify the underlying cause, as successful treatment of the underlying condition may eliminate AF in some cases 2, 1. For example, treating hyperthyroidism, sleep apnea, or achieving weight reduction can significantly reduce AF burden 1.

The presence of multiple risk factors has an additive effect on the perpetuation of AF, and early intervention targeting modifiable risk factors may slow or prevent progression 1.